Patient Age in Spitz Nevus and Malignant Melanoma Implication of Bayes Rule for Differential Diagnosis

Department of Pathology, Veterans Affairs Medical Center, Durham, NC 27705, USA.
American Journal of Clinical Pathology (Impact Factor: 2.51). 07/2004; 121(6):872-7. DOI: 10.1309/E14C-J6KR-D092-DP3M
Source: PubMed


In the differential diagnosis of Spitz nevus vs malignant melanoma, patient age provides a critical piece of clinical information, because Spitz nevi occur mostly in children and melanomas occur mostly in adults. Nevertheless, there is overlap in the age distributions of Spitz nevus and melanoma. The issue to consider is how these age distributions and their governing probability densities can impact the a priori probability that a lesion is a Spitz nevus vs a melanoma. Herein I introduce a quantitative approach that uses Bayes rule together with previous published data on the age distributions in Spitz nevi and melanoma. The resulting algorithm yields plots and a table of predictive a priori probabilities of Spitz nevus, given patient age occurring within narrow intervals, and I believe these provide useful guidelines for using age in the differential diagnosis of Spitz nevus and malignant melanoma.

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Available from: Robin T Vollmer, Mar 18, 2014
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    • "It is also known that polarizing specific white lines are more frequently seen in melanomas, which are invasive [5]. The likelihood of Spitz nevus decreases with increasing age [6], and some authors recommend the excision of all Spitz nevi at any age due the fact that the distinction from melanoma can be challenging dermatopathologically [7]. In the largest study evaluating PSWL, of the non-biopsied lesions, none of 9750 Clark nevi, 90 congenital melanocytic nevi (CMN), 168 intradermal nevi (IDN) and 15 blue nevi displayed this structure, while of the biopsied lesions one of 20 Clark nevi, two of 10 IDN and none of one CMN displayed PSWL [5]. "
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    ABSTRACT: We report a case of a melanoma arising in a congenital-type compound nevus, which was excised because it was observed by both the patient and the treating dermatologist to have changed. Because the lesion was routinely photo-documented with both polarized and non-polarized dermatoscopy images prior to excision, these images were available for subsequent examination. Matched images are presented in what appears to be unique in the published literature: polarizing-specific white lines are identified as a compelling clue to the diagnosis of melanoma in a lesion that contains no clues apparent in the non-polarized image. Dermatopathology images reveal that the melanoma is arising in conjunction with a congenital type nevus. As expected, dermatoscopic polarizing-specific white lines are evident on the melanoma but not the nevus, and while a possible explanation is discussed, this remains speculative.
    01/2014; 4(1):83-7. DOI:10.5826/dpc.0401a14
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    ABSTRACT: Differentiating Spitz nevus from malignant melanoma is difficult and controversial. Despite helpful lists of differential diagnostic features, uncertainty about the diagnosis often provokes some to stain the tumor for MIB-1 antibody to Ki-67 and measure the proliferation index (PI) of the tumor. Of the many reports about MIB-1 PI in Spitz nevi and melanoma, none have consolidated the information to provide guidelines for the predictive probability that a lesion is a Spitz nevus, given that the MIB-1 PI falls into a certain interval. The present study used previously published data and exponential and gamma probability density functions to model statistical distributions of PI, respectively, in Spitz nevi and melanomas and Bayes rule to estimate the predictive probability that a lesion is a Spitz nevus, given an observed PI. Results indicate that PIs more than 10% favor a melanoma diagnosis and PIs less than 2%, Spitz nevus. PI values between 2% and 10% yield various predictive values for Spitz nevus, depending on the a priori probability that the lesion is a Spitz nevus. The algorithm tabulates guidelines for the predictive probabilities of Spitz nevus given an observed PI.
    American Journal of Clinical Pathology 11/2004; 122(4):499-505. DOI:10.1309/MFFF-06D5-CYXR-2F8T · 2.51 Impact Factor
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    ABSTRACT: Spitz nevus is a clinico-pathologic entity that can cause diagnostic concern, particularly in adults. Many studies have been performed to establish reliable histologic criteria, in the attempt to differentiate this lesion from melanoma. A series of 247 Spitz nevi, 6 of which were formerly classified as melanomas, were reviewed for clinical and histopathological parameters. Patients older than 20 comprised 66% of cases, with a predominance of women. The lower extremity was more affected in females of any age, whereas the trunk was more frequently involved in men over 40. Histopathologic examination showed the following differences among Spitz nevi related to age: acanthosis, parakeratosis, pagetoid infiltration, and Kamino bodies were more frequent in young people, whereas multinucleated melanocytes were more frequent in adults. The latter also had lesions that were less pigmented, with less maturation and more desmoplasia. At a mean follow-up of 94 months (range 52-172), recurrence at the site of biopsy or metastases were absent. In our study, a greater proportion of Spitz nevi occurred in adults than in previous series. Moreover, the relative incidence of Spitz nevus compared with melanoma in our population was higher than in other studies. Histopathologic criteria elaborated to diagnose Spitz nevus, applied to our cases, appeared reliable, allowing a correct diagnosis, even in adults.
    American Journal of Dermatopathology 12/2005; 27(6):469-475. DOI:10.1097/ · 1.39 Impact Factor
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